Real world.
Nope. You will not see a difference.
I am running Kingston HyperX Black 1600 4x4 from a 6x4 kit.
$240.00 for 1866 4x4 kit would have very little increase, I would not detect.
Them money would be better spent on Video card upgrade.
I run my 1600 memory at 1066 on my x58 system. I never notice a difference.
To reach anything over 1866 (ie 2400) on a x79 system requires overclocking.
Merry Christmas and Happy New Year